Method of paper drying and apparatus therefor



Ndv. 20, 1928. 1,6'1','9 30 A. v E. MONTGOMERY METHOD OF PAPERDRYING.AND APPARATUS THEREFOR Filed July 21, .1927

a I e aINVENTOR,

ADMJDWMr amdunr 12M. ATTORNEYS.

Patented Nov. 2O, 12,

area

ALVIN E. MONTGOMERY, 0F OAK PARK, ILLINOIS.

IJIETHOD OF PAIER DRYING- AND APPARATUS THEREFOR.

Application filed July 21,

This invention relates to paper manufacture, and more particularly to aprocess and apparatus for dryingthe moisture from thethe dryingoperation consists in passing the formed web over a plurality of heatedrolls, With which it is maintained in intimate contact, often by meansof a canvas belt or felt.

The paper as it comes from the paper making machine may contain aboutone to two and a half pounds of water for each pound of dry paper, andone of the serious problems in drying the paper is the furnishing of theheat necessary to evaporate this moisture and the imparting of this heatto the paper Without the employment of unduly high temperature. As aresult, in the practical manufacture of paper, especially thin paper,produced at high speeds, it sometimes happens that as many as onehundred and fifty or eighty of these drying rolls are required, and aseach of them is several feet in diameter and frequently eight totwenty-two feet long,

' the space occupied by the drying machinery alone is considerable.Furthermore, the driers must be constantly maintained at or above steamtemperatures, and the consumption of heat is necessarily large. v

In this customary method, as will be obvious, the heating is performedonly while the paper is in contact with the rolls and hence it is notcontinuous, as a cooling effect necessarily occurs .in passing the webfrom one roll to another. Y

Moreover, the drying is performed under atmospheric conditions, theactual evaporation taking placeat slightly under the boiling point ofwater, and the vapor slightly cools as it leaves the web and comes intocontact with the air. Under such conditions, the quantity of moistureevaporated is very largely affected by the saturated condition of theair immediately surrounding the paper due to the moisture which has beenpreviously driven off from the webs. Furthermore, the heat absorbed bythe vaporization is largely if not entirely lost and dissipated exceptas it may be partially utilized for ventilation and heating purposesunder some modern systems.

It is an object of the present invention to 1927. Serial No. 207,463.

overcome many of the difficulties and objections attendant upon suchmethods of drying, and not only to simplify and render the dryingmachinery more compact and less expensive, but to materially reduce thecost per ton of the drying operation, while at the same time to improvethe character of the' product.

More specifically, it is an object of this invention to effect thedrying of the paper more quickly and with less complication ofapparatus.

I have discovered that if paper be subjected to the direct action ofsuperheated steam that the drying is very much hastened and the dryingapparatus very much simplified. Also,

ifenough heat be supplied and so distributed as to maintain theatmosphere immediately surrounding the web at a temperature far abovethe boiling point of water at the pressure involved, in spite of theevaporation, the superheated steam atmosphere may, in fact, be producedfrom the moisture in the paper itself.

If such operation be carried on in an enclosure it maintains in theimmediate vicinity of the paper an atmosphere which in effect is verydry, and which is higher in temperature than the paper and higher thanthe boiling point of the contained moisture, and thus serves to heat anddry the paper continuously and very rapidly. This is particularly trueas compared with the present practice in which the moisture, evaporatedfrom the rolls at a temperature higher than the surrounding atmosphere,cools immediately as it leaves the web, producing a layer of air in theimmediate vioinity of the paper which is supersaturated with moisture.

It is a further object of the invention greatly to'economize the cost'ofdrying by reducing the amount of heat. In the drying of paper, the heatis largely consumed by furnishing the latent heat of the moisture to beeliminated. As heretofore conducted, once this heat was absorbed, itwas. not again utilized in the process. In accordancewith thisinvention, however, provision is made whereby the heat absorbed in onestage of the drying operation is conserved in a form available .forreuse at another stage. This may be ac ---ing at a lower temperature.The drying by v steam to another portion of the apparatus to tion t beused as a heating medium therein.

The invention accordingly comprises the steps hereinafter described andthe relation and order of one or more of them with respect to each ofthe othersand the apparatus embodying the features of construction,combination of elements and arrangement of 3 parts which are adapted toeffect suchsteps, all as exemplified in the following detaileddisclosure and the scope of the application of which will be indicatedin the claims.

The drawing is a diagrammatic perspective of an apparatus-embodying theinvention and with which theprocess may be carried out. The web formingmechanism itself is not illustrated as it forms no specific part of thisinvention.

In feeding the paper'to an atmosphere of superheated steam, I find itdesirable to have it enter that atmosphere already considerablypreheated, since if it enters cold-,it must be heated by the steam andthis causes the precipitation upon it of moisture which must bereevaporated before further drying can begin. In the preferredembodiment, therefore, the invention contemplates a preliminary heatinas well as intensive drying. It is desirable a so to add a third stagein which the paper is assed over heated rolls while still slightly am inorder, to insure that it shall be finished at and smooth. This divisionof the invention also facilitates the recovered from the intensive drierto Be used to effect the 'preliminar heating or the final dryingor both.It is esirable to so propore parts of the apparatus that all of theavailable heat carried by the superheated steam will be utilizedin otherstages.

' The apparatus, herein illustrated, therefore, inc udes an initialstage 1, comprising drying rolls and an intermediate stage 2 comprlsingthe drier in which the intensive drym by superheated steam is carriedon, and a al stage 3 comprising drying and finishing rolls. The papercoming from the machine as shown at 4 is conducted successively may bethrough these apparatus.

In the specific form of apparatus illustrated the initial driercomprises a plurality of rolls 10, each of which preferably has a thincircumferential wall and insulated ends 11. Means are provided forfeeding steam 'into these rolls by an inlet pipe12 while pipes 13 serveto permit the exit of exhaust steam and condensed water. Any convenientmeans rovided associated with these rolls for caus ng the water to passout of outlets 13.

The various rolls 10 are arran ed on parallel axes, so that the papermaybe threaded over them, preferably supported b the usual canvas stripsor felts 14 and 15. hese felts have herein been shown diagrammaticallyonly, as their specific construction forms no part of this invention.The various inlets 12 may be connected to a header 16 receiving steamfrom a supply pump 17 from the chamber of the second stage,-as will behereinafter described. These rolls serve to raise the temperature of thefreshly made pa er and to evaporate therefrom an appreciab e quantity ofthe contained moisture, and to dry it to the point where it can supportits own weight.

* In practice the paper may,leave these rolls at about 160 degrees F.During this first stage of drying, it may be desirable to maintain thepaper under tension.

'designedas to admit the web with the minimum infiltration of air.

Within the chamber 20 is provided means for maintaining theatmosphere'in the immediate vicinity of the paper at a temperature verymaterially above the boiling point.

Since this results in a very large evaporation with a consequent coolingeffect on the web,

it is desirable that the heating means be distributed to affect the webas intimately as As illustrated, the heating means possible.

comprises a plurality of layers of pifpe 23,:

each layer being arranged in zigzag rmation extending from an inletheader 24 to an exhaust header 25.

A plurality of rollers 26 are arranged at each end of the bank to permitthe web to be threaded back and forth between thelay ers, I i

the rollers being arranged to receive the paper coming from between twolayers and to reverse it to be fed backward between the next two layers.

If desired, the web may be supported at this stage also b felts or wires27 i and 28., The pipes 23 are esigned to receive steam at a hightemperature, as for example 200 lbs. pressure. This, allowing formefliciencies of heat transfer, and in spite of the cooling effect ofthe evaporation, maintains the temperature within the chamber in theneighborhood of 260. This corresponds to a superheat of substantially 48if the pressure within the chamber be substantially atmospheric. r

The drying effect of such an atmosphere is in excess of what can beobtained in-any practical manner at temperatures approaching the boilingpoint. This steam either as it enters or leaves the header 25, may bereduced to alower pressure, as for example 20 lbs. This causes are-eva-poration of an apprecibe carried by pipes 37 to a header 38. In

the form illustrated the drier 3 may be enclosed within the chamber 20.w

The exhaust from the chamber 20, comprising the superheated steam givenofl from the webs, may be utilized to heat the initial drying rolls. Tothat end it may be led by j conduits 40 and a1 from the casing to thefan 17 to be forced by it into the initial drying rolls. Obviouslyseparate casings may be employed for the driers 2 and 3 if desired andalso superheated steam from the intermediate drier 2 may be utilized toheat either the initial rolls or the final rolls or both, depending uponthe quantity of steam available and the effect desired.

With the process above described the web is subjected to the highesttemperature in the second stage drier 2, and it is preliminarily heatedby the first stage drier 1. Furthermore, as the web leaves the drier2"and it passes into drier 3, it is not necessarily maintained at thehigh temperature even though both are enclosed by one casing.

It will thus be observed that the initial stages of heating and thefinal stages are both at lower temperature .than the intermediate.

It will also be seen that the water evaporated from the paper is at alltimes kept completely separated from the boiler steam used as theprimary'source of heat so that there can be no contamination of theboiler Water by pulp or impurities. The water condenser in the drier- 1,therefore, serves as a source of clean hot water for re-use in the papermatting process, thus still further conserving it 'heat. The condensedboiler water from the final drying rolls ,and the condensate from theheader 25 may be used as a source of boiler feed if desired.

By the above process it will be clear that the drying is accomplishedmuch more-intensively with a very large saving in apparatus andconsequent overhead expense in the plant. This may also obviously beutilized to increase the speed of paper manufacture and thus the plantcapacity.

A practical illustration of the operation of such a plant may be asfollows 1 We may assume that the sheet comes from the paper makingmachine with somewhat more than two pounds of water per pound of drypaper, of which two pounds are to be evaporated. This means, in a fiftyton plant,

the evaporation of 139 pounds of water per minute. The plant may bedesigned to evaporate 46.3 pounds in the first drier, 86.2 pounds in thesecond drier and 6% pounds in the third drier. The steam may be suppliedto the coils of the second stage-at 200 pounds per square inch, whichmay maintain the temperature of the steam generated within thechamber 20as it is exhausted from the chamber at about 232 degrees Fahrenheit,although a somewhat higher temperature will be produced at the webs.These correspond to steam consumption within the plant of substantially1.74 pounds of steam per pound of paper dried, which is about one halfthe steam used in the customary paper drying'machines which, at presentcommercial rates, is a very material saving in steam consumption alone.

Furthermore, by reason of the fact that the apparatus is more compactand the heat more nearly concentrated on useful Work, it would be clearthat there would be less parasitic radiation of heat into the room. Thisprocess, in addition to enabling the capacity of the mill to beincreased with an improved product, also reduces the steam capacity perpound of paper produced to substantially one-half that required byexisting processes, and at the same time frees the mill from a largepart of the space now occupied by the present cumbersome dryingmachinery. I

' Since certain changes in carrying out the above process and in theconstructions set forth, which embody the invention may be made Withoutdeparting from its scope, it is intended that all matter contained inthe above description or shown in the accompanying drawing shall beinterpreted as illustrative and not in a limiting sense;

It is also to be understood that the following claims are intended tocover all of the generic and Specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween. V Y

Having described my invention, what I claim as new and desire to secureby Letters Patent, is:

1. In an apparatus for drying paper, in combination a plurality ofdrying drums, a drying chamber having surfaces therein heated by hightemperature steam, a plurality of finishing drying drums and means forpassing steam from said surfaces to said finishing drying drums wherebythe latter areheated by the steam which is cooled by said surfaces, andmeans for subjecting the paper to the influence of said surfaces togenerate steam therefrom and means for conducting said generated steamto said initial drying drums.

2. A process of drying paper consisting in suppl ing steam to heatingmeans, formin super eated steam, using said superheate steam forpreliminary heating purposes and withdrawing the steam from said meansfor use in other heating means.

3. A process of drying paper consisting in subjecting the paper to steamheated coils in steam from the coils to complete the process.

5. An apparatus for drying paper comprising first means adapted to beheated by steam under pressure, means for subjecting a web of paper tosaid first means whereby the moisture from the-web will beconverted-into su per-heated steam, means for usin said superheatedsteam to preliminarily heatanother portion of the web in its passage tothe first means, and finishing means for utilizing the steam from saidfirst means at a diflerent pres- I sure.

6. In a system for drying paper, preheating means for evaporatingmoisture from a web of paper by utilizing superheatedv steam formed in amain heating chamber, heating apparatus in said chamber utilizing steamunder pressure to cause the evaporation of moisture from the web and thetransformation of said moisture to superheated steam for the preheatingmeans, and finishing means employing steam fromthe heating apparatus ata lower pressure to cause the re-evaporation of condensed water fromsaid steam and to fur-then heat the web to substantially dry condition.1

7. In a combination of apparatus for drying paper, a chamber, heatradiation means in the chamber, means for moving a web of paper inassociation with said radiation means to convert moisture in said webinto superheated steam, other heating means in said chamber adapted tobe heated by steam from said radiation means, the web being adaptedcontact therewith to become substantially 8. In a combination ofapparatus for drying paper, a chamber substantially steam tight, aplurality of heating means in said chamber, means for movinga web ofpaper through said chamber in intimate association with said heatingmeans, heating drums in said chamber utilizing steam from said firstmeans at a lower pressure, heating drums without the chamber adapted toutilize superheated steam formed in the chamber.

9. In a combination of apparatus for dry ing paper, a chambersubstantially steam tight except for an inlet and an outlet for a 'webadapted to pass therethrough, means heated by steam at a certaintemperature adapted to dry the web passing through the chamber and formsuperheated steam from the moisture evaporated from the web, otherheating means in the chamber heated by steam from said first means at alower temperature, the web adapted to contact therewith to be furtherdried, the superheated steam in said chamber being adapted to servepreheating means without the chamber for initially heating theweb priorto its entering the chamber.

testimony whereof I aflix my signature.

ALVIN E. MONTGOMERY.

